The effect of cortisol on the activity of glutamate-pyruvate transaminase and the formation of glycogen and urea in starved rats

Abstract

A single subcutaneous injection of cortisol suspension into starved rats increased the 24 hr. urea excretion over a wide dose range (2.5-40 mg./rat). At the highest dose there was a twofold rise in urea excretion with no change in plasma or tissue urea concentration. At all doses cortisol increased liver glycogen within 2 hr. after injection. The rate of glycogen deposition was not affected by the amount of steroid injected but larger doses maintained the process for longer periods. With the higher doses liver glycogen amounted to about 6% of the wet weight of liver 24 hr. after injection. Liver glutamate-pyruvate-transaminase activity was increased only after a lag period. An increased dose reduced the lag period without affecting the rate of increase of enzymic activity. Two hours after a subcutaneous injection of [3H]cortisol (10 mg.) the plasma radioactivity was equivalent to about 50 xg. of steroid/ml. Thereafter plasma radioactivity fell exponentially whereas liver radioactivity dropped at a linear rate. The apparent half-life of the injected steroid was approximately 6 hr. and 24 hr. for plasma and liver respectively.